Human serum contains a unique set of proteins with affinity for DNA. The two predominant proteins of this set, DBP-1 and DBP-2, are now purified to homogeneity as is the malignancy-associated DNA-binding protein, C3DP. This proposal outlines plans to conduct an extensive genetic, biochemical, physicochemical, and physiological study of these proteins with the goal of determining the functions of these proteins in serum. A comprehensive search for genetic polymorphism and hereditary deficiency of DBP-1 and DBP-2 will be undertaken. DBP-1 and DBP-2 will be further characterized as to lipid and carbohydrate content and a study, by limited proteolytic digestion, will be initiated to determine the regions of the molecules responsible for DNA-binding capacity. The nucleic acid binding specificity of each protein will be determined by binding studies with synthetic oligonucleotides and specific fractions of unique and repetitive human DNA, and by the ability of the proteins to protect restriction sites on characterized DNAs. Studies of the cell location, metabolism and biosynthesis of DBP-1 and DBP-2 will be undertaken. Cultured cell lines and human tumor cell lines of various origins will be investigated for production of these proteins by radioimmunoassay and indirect fluorescence techniques. An in-depth investigation of the minor species of serum DNA-binding proteins and their relationship to chromatin-associated proteins will be initiated. Minor species of DNA-binding proteins will be studied as possible indicators of disease states. Sequence analysis of C3DP and further physicochemical characterization of the DNA-binding forms of this molecule will be aimed at an understanding of the mechanism by which this molecule is generated in the serum of cancer patients. A large scale screen of cancer patients for C3DP levels with long-term follow-up is planned to verify the prognostic value of C3DP determinations.